For a very long period of time roofing panel manufacturers have attempted to provide panels which must deal with a number of problems related to materials used, installation costs and performance after installation. A major problem area has always been in providing edge joints between roofing panels which will meet a number of important criteria as discussed below.
Difficulties pertaining to materials used have tended to change with the availability of materials and current architectural trends. For example, the light sheet metal which is currently widely used presents much different considerations from those which applied to heavier metal panels. For example, the edge treatment of the light metal panels must be roll formable rather than extruded. Many older edge treatments are not roll formable.
The strength and integrity of the edge joints between panels is clearly a very important consideration. The joint in particular must be such that it will not inherently give a loose joint nor will it over a period of time result in a loosening of the joint. As above, this aspect requires a much different treatment in dealing with light metal panels.
Furthermore, not only must the joint be physically strong, it must also be of such a nature as to be weather tight. This is of course of particular significance in the roofing context.
Labour costs are a major factor in construction and the ease and speed of installation are further important factors. The edge treatment of the panels is a key consideration in this regard.
Finally, all of the above requirements must be met while still providing a finished roof which is aesthetically pleasing.
These factors are not always easily reconciled. For example, light metal is relatively weak and particular attention must therefore be given when using that material to the strength of the joint.
To date a completely satisfactory joint for use with light metals has not become available.
Against this background the present invention provides a roof panel having an edge treatment which produces a joint which meets the above criteria.